Final answer:
A horizontal circular cross sectional jet is a jet with a circular cross-section oriented in a horizontal plane, which corresponds to option 1 in the choices provided.
Step-by-step explanation:
The description of a horizontal circular cross sectional jet refers to a jet with a circular cross-section that is oriented in a horizontal plane. This is consistent with option 1 in the list of choices provided in the question. The term "transverse plane" or "horizontal plane" is used in various fields, such as physics and anatomy, to describe a plane that cuts through an object, dividing it into upper and lower portions. In this context, imagining a jet moving through the sky, if we consider a plane that slices horizontally through the jet, we would get a circular cross-section of the jet if the body of the jet is circular in shape. This concept is similar to the way conic sections like circles are formed through the intersection of a plane with a cone.